Alright, let's solve this problem step by step. We have 894 and 105 and we're adding them together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 9 & 0 in column 2 and get 9.

Step 3: We'll start by adding the digits 8 & 1 in column 3 and get 9.

So, 894 + 105 = 999.

